Carbon brush for collector

ABSTRACT

A carbon brush for a collector has a recess which is filled with a layer of galvanically applied, copper plating, in which at least one longitudinal wire is provided as a connecting conductor, which is mechanically and electrically linked with the brush through being embedded in and completely surrounded by the copper layer.

BACKGROUND OF THE INVENTION

The invention relates to the manner in which an electrical lead whichextends over the length of a carbon brush is attached to the brush.

In a conventional carbon brush known from German utility model 8,716,985the connecting lead is formed as a strip of woven metal fabric or metalfoil which is secured to the brush by mechanically clamping it in adovetailed recess of the brush. The lead is mechanically andelectrically connected to the carbon brush, in part by clamping it inthe recess, and in part by a galvanically applied metal layer whichoverlays the lead. However, the strength of the connection between thelead and the brush is dependent on production tolerances. These mayfluctuate over the length of the brush, thus rendering it difficult toobtain precise values for the strength of the mechanical connection andthe resistance of the electrical connection.

German patent publication DE-OS 34 05 674 discloses a carbon brush whichhas a metallic plating that coats the underside or a groove in theunderside of the brush. The lead, in the form of a strip of wovenmetallic fabric or a metal foil, is soldered to the plating on theunderside of the brush. Soldering involves, however, an additionalmanufacturing step. Moreover, the soldering temperature producesstresses between the metallic layer and the underside of the carbonbrush as a result of differing rates of thermal expansion. This can leadto a separation of the metallic layer.

SUMMARY OF THE INVENTION

An object of the present invention is therefore to develop a carbonbrush of the aforementioned kind which has an improved electrical andmechanical connection for the lead of the brush.

In accordance with the present invention the electric lead is notclamped into a recess in the carbon brush, but rather is embedded in ametallic plating which fills the recess. This offers not only theadvantage of an improved mechanical and electrical connection betweenthe lead and the carbon brush, it also eliminates the need to conformthe shape of the lead to the shape of the recess, and the need forspecial pressure-applying tools for clamping the lead in place. It isnot necessary to construct the lead in the form of a strip of metallicfabric or foil. Instead, the lead may be a single wire or multiplewires.

BRIEF DESCRIPTION OF THE DRAWINGS

Two embodiments of a carbon brush constructed according to the presentinvention are shown in cross-section in the drawings.

FIG. 1 is a side elevational cross-section through a carbon brushconstructed in accordance with the present invention and illustrates howthe electrical leads are attached to the brush by electrical plating;and

FIG. 2 is an elevational view, in section, similar to FIG. 1 andillustrates another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a carbon brush 1 with a recess 3 on its underside togetherwith metal plating 5, preferably of copper. The metal plating completelyfills recess 3. Wires 7 are imbedded in metal plating 5 in the area ofrecess 3. Wires 7 together with metal plating 5 define a current path inthe longitudinal direction of carbon brush 1.

FIG. 2 shows a woven metal fabric strip 9 which is disposed in recess 3of carbon brush 1. It is held in place not by being clamped in place,but rather by being embedded in metal plating 5.

The production of a carbon brush in accordance with the presentinvention requires a first plating step during which a layer of copperis plated over the inner surfaces of a recess, which was previouslyformed by milling or during press molding of the brush. Next the lead,in the form of one or multiple copper wires or a copper strip 9, isplaced into the recess. During a second plating step the underside ofthe carbon brush and the lead are coated with a second layer of copperso that it bonds with the first layer of copper and fully embeds orenvelops the lead.

The carbon brush of the present invention may be supported over itslength in a conventional manner with a support. At least one end of thesupport includes an electrical connector which is mechanically attachedand/or soldered directly onto metallic layer 5 and/or wires 7 or metalstrip 9. The carbon brush of the present invention is particularly wellsuited for use with a support made partially or entirely of plastic.

What is claimed is:
 1. A carbon brush for a current collector comprisingan elongated carbon brush having a longitudinal recess extending alongan under side of the brush, an elongated electrical lead located in saidrecess and extending along the length of the carbon brush, and a copperplating galvanically applied to the under side of the brush, said copperplating filling the recess and completely embedding and surrounding theelectrical lead in the recess for mechanically and electrically securingthe lead to the carbon brush along the length thereof.
 2. A carbon brushaccording to claim 1 wherein the lead comprises multiple conductors. 3.A carbon brush according to claim 1 wherein the lead comprises a singleconductor.
 4. A carbon brush for an electrical current collectorcomprising an elongated carbon brush with a longitudinal recessextending over the length of the carbon brush and formed in an underside thereof, an electrical lead completely disposed inside the recessand extending in the recess over substantially its full length, and acopper layer galvanically applied to the under side, filling the recess,completely embedding the lead in the copper layer and forming a solemechanical and electrical connection between the carbon brush and thelead.
 5. A method for manufacturing a carbon brush for a collector, thebrush being elongated and including an under side defining a recessextending substantially over the full length thereof, the methodcomprising the steps of first electroplating a copper layer oversurfaces of the brush defining the recess; thereafter placing at leastone elongated conductor completely inside and so that is extends oversubstantially the full length of the recess; and thereafterelectroplating a further layer of copper while maintaining the lead inthe recess, the electroplating step including the steps of fullyembedding the lead in the further copper layer and simultaneouslybonding the further layer to the first applied layer so thatelectroplated copper forms the sole electrical and mechanical connectionof the lead to the brush.